Sugar is a key factor, significantly affecting fruit flavor quality through sucrose metabolism and accumulation. This study investigated the effect of short-day shading on the accumulation of soluble sugars in citrus fruits by using 'Nanfeng' tangerine (Citrus reticulata cv. Nanfeng) as materials. Results revealed that using a black net with 12 % light transmittance for 18-day shading remarkably increased soluble sugars and decreased starch content in fruits. Moreover, expresion levels of two cell wall invertase genes (CwINV6/7) and one sucrose synthase genes (CsSUS6) in the segment membrane (SM) were increased significantly at 18 DAS. On the other hand, in juice sacs (JS), expression levels of vacuolar invertase (VINV), five sucrose synthase genes (CsSUS1-5), two sucrose phosphate synthases (CsSPS1/3), some sugar transporter genes including STP7, SUT1/2/3, two SWEET genes (SWEET5/10), two vacuolar glucose transporter genes (VGT1/2), two tonoplast monosaccharide transporter genes (TMT1/2), and two citrus type I V-PPase genes (CsVPP1/2) were increased significantly at 18DAS as compared to control. Furthermore, starch degradation related gene ISA3, BAM3, GWD and PWD were also significantly induced by 18-day shading. Overall, this study suggested that short-day shading (12 %) enhances soluble sugar accumulation in citrus fruit, primarily by promoting starch degradation and soluble sugar storage in the JS, except for the increase of sucrose distribution to the fruits.